1. Field of the Invention
The invention relates to a method of identifying the availability and the location of information streams, representing services such as data or radio or television signals, transmitted over one of a multiplicity of channels, in which at least one of these channels includes multiplexed information streams corresponding to a plurality of these services.
The invention also relates to an apparatus for transmitting such information streams along with availability and location information, and an apparatus for receiving selected services and identifying others which are available. The invention is particularly applicable to systems for simultaneously transmitting a multiplicity of signals for different services, using a number of different frequency bands, time-division-multiplexed channels in at least some of the bands, and time-division multiplexed services in at least one of the channels. Receivers of different types and capabilities will be used; some may have the capability of processing and utilizing most or all of the different services, while others may be able to utilize only one type of service having different programs or data files available on different channels.
In any systems of this general type, it is often difficult or expensive to provide a user with up-to-date information describing the services now available which this receiver can utilize, and their addresses (band, channel and service identification number).
2. Description of the Prior Art
The use of one channel in a cable TV system, for transmitting a schedule of programs available at that time, and for the next few hours, is well known. However, this requires that the user switch the receiver to the schedule channel, so that viewing of the currently watched program must be interrupted unless the receiver has Picture-in-Picture capability with sufficient legibility. To select a different program from that being watched, the user must use the same channel selector. If a VCR is to be programmed to receive a selected program in the future, in the event that the cable system finds it necessary to change the channel allocation or programming schedule, there is no way that the VCR can automatically reset itself to record the desired material at a different time or via a different channel.
U.S. Pat. No. 4,706,121 provides a broad description of electronic TV guides. However it does not disclose any way to locate a particular program in a multi-layer multiplexing system, such as one having both frequency and time division multiplexing.
U.S. Pat. No. 4,977,455 discloses a system enabling a user to cause a VCR to record program material broadcast at a time in the future, in response to a cue presented on the TV screen during viewing of a primary broadcast, without the viewer directly entering time and channel information into the VCR control. During the primary broadcast, data including the time and channel information for a related future broadcast are multiplexed with the primary broadcast signal. The system decodes the data, to present an on-screen cue to the viewer. The user can cause the system to store the relevant time and channel information, for automatic future recording.